(a) Field of the Invention
The present invention relates to a liquid crystal display (LCD) and a driving method thereof, and more particularly, to an LCD capable of transmitting data at high speed.
(b) Description of the Related Art
Liquid crystal displays (LCDs) are widely used such as in flat panel displays. An LCD generally includes two panels having a plurality of electrodes for generating an electric field, a liquid crystal layer therebetween, and two polarizers attached to outer surfaces of the respective panels for polarizing light. The brightness of light generated out of the LCD is controlled by applying voltage to the plurality of electrodes to rearrange liquid crystal molecules. A plurality of thin film transistors (TFTs) for switching the voltage applied to the plurality of electrodes are formed on one of the panels of the LCD.
A display area is generally located in the middle of the panel having the TFTs for image display. In the display area, a plurality of signal lines such as a plurality of gate lines and data lines are formed in row and column directions, respectively. A plurality of pixel electrodes are also formed in respective pixel areas defined by intersections of the gate lines and the data lines. The TFTs control data signals are transmitted from the data lines and the data signals are output to corresponding pixel electrodes responsive to gate signals transmitted from the gate lines.
A plurality of gate pads and data pads are formed at the periphery of the display area, each of the plurality of gate pads and data pads is connected to a corresponding gate and data line. The pads are directly connected to external driving ICs and provides external gate signals and data signals to the gate lines and the data lines, respectively.
A printed circuit board (PCB) for gate signals and a PCB for data signals are electrically connected to the TFT array panel via a plurality of the driving integrated circuits (ICs). Each driving IC is mounted on a flexible printed circuit (FPC) film which is attached to the TFT array panel.
However, this structure has disadvantages in that the size of the FPC film is large and electrical contact between the driving IC and FPC film may be poor.
A chip on glass (COG) may be used to alleviate some of the above problems. In the COG structure, driving ICs are directly mounted and the connection between driving ICs and PCBs is made by FPC films.
However, other disadvantages remain, for example, the COG structure involve the expensive FPC films, require a large amount of space for connecting the FPC films to the driving ICs, and still may have poor contact between the FPC films and the driving ICs.
One proposal to solve the above disadvantage includes a structure having only one of the driving ICs connected to one FPC film. In such structure, data signals from the FPC film enter into the data driving IC connected thereto and are transmitted to the next data driving IC and so on by shift operations of the data driving ICs connected in parallel. However, in such structure the level of data signals becomes lower due to the resistance of the connected wires.
Accordingly, a need exists for a method for driving a liquid crystal display at high speed, and minimizing the number of films used for transmitting and connecting the printed circuit board with the driving ICs.